Spring dowel



Feb. 11, R. c. YEOMAN SPRING DOWEL Filed Dec. 17, 19157 w m 0 Ms M A m a .w 5 u WO w V4. m n

Patented Feb. 11, 1941 UNITED STATES PATENT OFFICE Claims.

My invention relates to the construction of bridges, masonry and concrete structures, and particularly to the building of concrete pavements, and more particularly to an improved 5 load transmission unit using a spring dowel embedded in and anchored to the adjoining structures.

The primary object of my present invention is to provide a method for transmitting a concentrated load across the space intervening between adjoining concrete slabs, whereby a plurality of spring dowels spaced in series and at intervals along the slab edge will support the slab .edge against transverse local bending when acted upon by a load applied to one slab and over any one of the dowels in the series; and further,

To produce a unitary or one piece structure with the resultant elimination of sliding parts, and a structure which will be self aligning and adjust .itself to the irregularities presented in field assembly occasioned by improper placement or the misplacement of the dowel during the pouring, puddling, or vibrating of the plastic concrete; and

To provide a structure which is not susceptible to excessive corrosion or freezing due to erosion or corrosion of the dowel; and

i To eliminate greasing and the problem with friction as now encountered in structures of this aoz To maintain a constant predetermined pressure at the normal joint opening; and

a To provide a fixed resistance to the closing or" the joint between the adjoining sections of concrete; and

To provide for the elimination of tension in the body of the receding concrete slabs; and

To provide a structure whereby a hinge joining the faces of the opposing slabs frees the slab ends allowing sufiicient movement to cut down or reduce the warping stresses inherent in the unequally heated or wetted slabs; and

To provide an inexpensive, simple, durable, positive action, single piece construction load transmission unit which requires no great skill or expensive equipment to install and which may be permanently sealed; a dowel means for holding the adjacent ends of the adjoining road slabs in surface alignment while providing for the rela- 50 tive expansion and contraction thereof.

My present invention has these and other objects, all of which are explained in detail and may be more readily understood when read in conjunction with the accompanying drawing 55 (one sheet) which illustrates a preferred embodiment of my invention, it being manifest that changes and modifications may be resorted to without departure from the spirit of the claims forming a part hereof.

In the drawing:

Fig. 1 is a perspective View of the spring dowel;

Fig. 2 is a vertical section through the ends of a pair of adjoining slabs with the spring dowel of Fig. 1', shown in elevation and illustrating 10 the application of my invention when the dowel is under compression;

Fig. 3 is similar to Fig. 2 showing the position taken by the dowel unit when the slabs have receded; and 15 Fig. 4 is a fragmentary view of the clip shown temporarily attached to the spring disk.

The structure illustrated involves the specific application of one form of my invention to a roadway slab. For purposes of description only, 20 I choose to so define my invention as applied to this particular construction; however, I wish it understood that my invention is equally effective when adopted or used in any poured or precast structure, whether it be a roadway slab, retaining 2 wall, swimming pool, reservoir, canal lining, warehouse floor, dock, industrial plant, sidewalk, driveway, airport runway, bridge, etc., for, as a matter of fact, it is applicable to an almost unlimited number of structures. And while I describe my invention in its preferred embodiment, it is to be further understood that the words which I use are words of description and not of limitation.

It is now my discovery that joints should offer 35 considerable resistance to closing so that the slab will be kept constantly under compression longitudinally to neutralize tensile stresses and strains caused by loads, warping, etc.; and

That the inaccurate positioning of dowels by present methods creates friction by binding which will develop between dowel and slab and establish serious tension stresses in the concrete slab; and

That the warping of the concrete slab caused 45 by unequal distribution of heat and moisture is sufflcient to cause binding of dowels with concrete or their bearings in a system of dowels perfectly aligned at the time of installation; and

That the necessary exposure to the elements of the bridging section of the dowel raises the question of both the durability and the danger of reduction in efliciency by corrosion; and

That either misaligned dowels at installation, or warped edges, causes dangerous concentration of stress at dowel points, likewise causes cracking of the slab longitudinally and spalling of V sections from immediately above or below the dowel (tunnelling).

Accordingly, my present invention is intended to avoid the objections incident to the common dowel and to provide for the improvements as above outlined.

My invention consists in spanning the space intervening between the adjoining end faces of adjacent concrete slabs with a series of relatively short dowel bars, positioned at substantially middepth of the slabs, parallel with the top surface thereof, normal to the plane of the joint, and spaced at regular intervals throughout the width of the slab, and also in the retaining of the slabs constantly under compression longitudinally in order to neutralize tensile stresses and strains.

I now employ a cylindrical dowel 5, which bridges the space 6 intervening between the end faces of the adjoining slabs l and 8, the dowel bar itself having its medial portion deformed and tempered to form a resilient spring-like section 9 here shown as a flat helical coil, the opposite ends of the dowel being firmly bonded in place in their respective slab sections 1 and 8.

* Fig. 3 of the drawing. The disk is then tem- In manufacture, the aligned anchoring end portions may be of the conventional dowel steel, round in cross section and having an end ll, of each welded to the resilient medial portion 9, the weld beingbuilt up in the form of a fillet 12.

The resilient spring like section 9 is here shown as a round disk cut thru from a point on the periphery to approximately the centerv of the disk and then warped so that the opposing faces l3 and It formed by the cut will be offset as shown Figs. 1 and 3. The dowel anchoring sections 55 are welded one to the section of the disk above the out and the other to the section of the disk below the cut as clearly shown by ill such as bitumen or cork, or the commonly accepted metal walled air cushion type of joint (not shown), as the joint structure as such forms no part of my invention.

f It is contemplated that the dowel member may be installed in the plastic concrete, the spring portion 9 being first prccompressed or put under restraint, the restraint being released when the concrete has set so that the slabs are immediately placed under compression for the purposes above outlined.

As an illustration, Fig. 4 shows the opposing faces l3 and M of the disk 9 brought together and a U-shaped clip l5 slipped over the disk to hold the faces l3 and I4 in aligned position. The

"clip I5 is removed once the concrete has set so that the resilient or spring section 9 of the dowel may be free to exert a pressure against the faces of the slabs and follow through as the slabs retract or move away from one another when increasing the space between the slab ends as shown at Fig. 3 and thereby keeping the slabs under compression and serving to neutralize the tensile stresses and strains caused by the loading of the slabs comprising the concrete road.

The foregoing discussion and the illustrations shown on the accompanying drawing describe my invention as applied in general to poured concrete cast in situ; and, whereas, I have not shown the specific structure, I wish it understood that my invention is equally applicable to precast concrete, art marble, imitation stone, glass, terra cotta and other similar products or combinations thereof.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In the art of road building, a dowel bar for connecting the adjoining slab sections at joint locations and presenting a shearing and bending resistance to deformation caused by loads imposed in a plane normal to its major axis, said dowel comprising a pair of axially aligned rigid members adapted to enter and have bearing in their related slabs, a distensible member connecting the rigid members, and locking means releasably engaging said distensible member.

2. A dowel bar as per claim 1 wherein the rigid members are afiixed to and form an integral part of the medially disposed distensible member.

3. In a concrete pavement or the like, the combination of a pair of concrete slab sections having their adjacent edges initially spaced from each other with a dowel bar for connecting the adjoining slab sections, said dowel comprising a. pair of aligned rigid members adapted to enter and have bearing in their related slabs, a distensible member connecting the rigid members, locking means releasably engaging said distensible member, wherein the distensible member occupies a position entirely within the space between the adjoining slab. sections.

4. In combination with a dowel as set forth in claim 3, a yieldable element positioned between the slab faces and sealing the space therebetween.

5. A dowel bar as per claim 1 in which the distensible member connecting the rigid members, comprises a relatively fiat circular disk partially cut through on its diameter, the adjoining faces of the out being initially offset from one another, and one rigid member being affixed to the face of the disk above the cut and the remaining rigid member being affixed to the opposite side of the disk and below the cut, said disk permitting the relative horizontal movement of the rigid members but resisting the vertical movement thereof.

' RAY C. YEOMAN. 

